This invention relates to a tank-mounted filling device particularly for liquefied gas, which comprises a housing mounted in the tank wall which housing is provided with a chamber and a supply duct opening therein whereon the supply line may be connected, and comprises a cut-off valve which is arranged inside said chamber, which valve has a head which cooperates with a valve seat on the duct end and closes off said duct with the end thereof in the closing position, but still leaves free in said position a space about said head in the chamber, said space extending down to the closed duct end, and has a piston-forming body which separates said space about the head from a backmost volume lying on that valve side removed from the duct, which valve is provided with a second duct which runs length-wise through the body and the head thereof and brings the backmost chamber volume into communication with the supply duct even in the valve cut-off position, which housing is moreover provided with at least one opening which brings the tank inner volume into communication with said space about the head and in the valve open position, also with the supply duct, and is provided with a third duct which brings the backmost chamber volume into communication with the tank inner side, which filling device comprises a spring which pushes the cut-off valve to the closing position, and comprises a valve controlled by a float mechanism inside said tank, which is mounted inside the third duct in the housing and cuts off said duct when the liquid inside the tank has reached a determined level.
Such a filling device is known from Belgian Pat. No. 871,180. In this device inside that duct which runs cross-wise through the cut off valve, is mounted a one-way valve which only lets liquid flow to the chamber backmost volume. When filling the tank, due to the pressure in the supply line being higher than the pressure inside the tank, not only the cut-off valve is open but also said one-way valve is open. The largest portion from the supplied liquid flows through openings which open on the chamber frontmost volume, into said tank. A smaller portion flows through that duct which runs cross-wise through the cut-off valve, and the third duct provided in said housing, to the tank. When the desired level, that is generally 80% from the contents for tanks for liquefied gas, has been reached, the supply is automatically stopped. The float mechanism then never holds the third duct open any more. Thereby the pressure inside the backmost volume inside said chamber, which no more communicates with the tank inner side, will rise until the cut-off valve is pushed back to the closed position by the spring acting thereon. At the same time, the one-way valve inside that duct running through said cut-off valve, will also be pushed to the closed position by a spring acting thereon. Due to both the cut-off valve and the one-way valve lying in the closed position, a relatively high pressure still remains active in the backmost volume of said chamber. There results that said known filling device cannot be used for draining liquid from the tank. Indeed when the drain cock is opened and consequently a low pressure is caused inside the supply duct, neither the cut-off valve nor the one-way valve will open as the pressure inside the backmost chamber volume is higher, namely equal to the pressure inside the gas tank when that valve controlled by the float mechanism inside the third duct from the filling device is open, and even higher still when with the highest liquid level inside the tank, said duct is still closed.
To be able to drain or draw off, a tank which is provided with such a known filling device, has to be provided with a special drain device which does of course increase the tank cost.
The invention has for object to obviate this drawback and to provide a tank-mounted filling device which does not only allow filling but also draining fluid from the tank through said supply duct.